Aqueous electrolysis cell for saline solutions, especially of alkali chlorides



E. KREBs TAL 3,399,131

ESPECIALLY 2 Sheets-Sheet 1 Aug. 27, 1968 AQUEOUS ELECTROLYSIS CELL FOR SALINE SOLUTIONS,

OF ALKALI CHLORIDES Filed Jan. 24, 1966 Aug. 27, 1968 E. KRL-:Bs ETAL 3,399,131

, AQUEOUS ELECTROLYSIS CELL FOR SALINE SOLUTIONS, ESPECIALLY OF ALKALI CHLORIDES Filed Jan. 24, 1966 2 Sheets-Sheet 2 P uw.

United States Patent Claims. (l. 21M- 220) This is a continuation-in-part of patent application Ser. No. 463,642.

The present invention relates to improvements for electrolysis cells for saline solutions (and in particular the aqueous electrolysis of alkali chlorides), in which the electrode surfaces are coaxial surfaces of revolution with a vertical axis, said cells being included in a general installation for electrolysis, which contains all the necessary accessories.

We have already described .in our application Ser. No. 463,642 of lune 14, 1965, entitled, Aqueous Electrolysis Cell for Saline Solutions, Especially of Alkali Chlorides, an installation for electrolysis of saline solutions, including such a cell combined with a decomposer device independent of the said cell.

As a matter of fact, the electrolysis of the brine in such a cell, which happens between the two coaxial electrode surfaces, amongst which one of them, namely the cathode, serves as a support for the ow of a thin layer of mercury, produces an amalgam between the mercury and the metal of the solution to be electrolysed.

The amalgam is directed towards the outlet of the cell, to be led into the independent decomposer.

The object of the present invention is to provide a cell similar to the one described in the above mentioned application, but which is combined with a decomposer; the operation and the principle of which are identical with that one described in the labove application, in order to realize a compact assembly, which reduces advantageously the bulk of the installation and the whole cost of the latter.

Another object of the present invention is to provide a device for electrolysis of saline solutions, which device can be utilized in cells operating at atmospheric pressure or in cells operating at high pressures which can reach l0 bars.

For this purpose, the device in accordance with the present invention is essentially characterized by the fact that the amalgam decomposer is placed coaxially with the main cell, the latter being surrounded by the former and that it comprises essentially a sheath of steel, which supports internally graphite pellets serving as decomposition grates for the amalgam which flows in the form of a thin lilm between said grates and the cathode of the main cell.

Other characteristic features and advantages of the present invention will be brought out in the description which follows below, prepared with reference to the accompanying drawings.

In the drawings:

FIG. l shows in vertical section an embodiment in accordance with the present invention of the assembly comprising the main cell and the decomposer.

FIG. 2 shows diagrammatically a view in elevation of a complete installation lin accordance with the invention, which includes the device shown in FIG. l.

The cell, shown in FIG. l, is constituted by the different components whose details are given hereinafter.

The anode 3 is in the form of va frustoconical shape.

It is made of metal and plated with a thin sheet of metal resistant to the action of the nascent chlorine.

An inner cone 24 (of aluminium, for example) distributes the electric current coming in through the conductors 8. The anode 3 is guided at its lower portion by its extension 9 and a packing gland 25. The cathode 1 is of steel. It receives the current by means of the conductors 2. The very thin layer of mercury 13 on the cathode 1 is supplied through an inlet conduit 11 (arrow F1) for the mercury, setting the ring 12 of mercury in motion. The mercury enters the electrolysis space through slot 27 between the cathode 1 and the ring 28, plated like anode 3 with a thin coating of metal resistant to nascent chloride. The amalgam formed by the mercury and the alkali metal of the chloride to be electrolysed leaves the apparatus (arrow F3) through the `conduit 15, after having been collected in the space 14.

The rich brine to be electrolyzed passes into the cell through the conduit 16 (arrow F3) and imparts a rotary movement to the iluid contained in volume 17. It then rises between the electrodes 1 and 3. In the space between extension 5 of anode 3 and ring 28 it encounters guiding vanes 29 which serve to maintain the rotational movement. The mixture of weakened brine and gaseous chlorine is collected in annular space 30 and leaves the apparatus (arrow F9) in the direction of a separator.

The amalgam decomposer is placed coaxially with the primary cell. Body or sheath 32 of the decomposer is made of steel and is supported by ring 26, while said body supports itself the primary cell. Graphite pellets 35 are fastened onto the bottom of the decomposer, and serve as decomposition grates. The very thin sheet of amalgam 37 owing on the wall of body 32 is supplied through the conduit 34 (arrow F2), by which the ring of amalgam 36 is set into movement. The amalgam liows down along the wall of body 32 and decomposes during its downward motion.

The regenerated mercury is collected in space 38 and leaves the apparatus through conduit 39' (arrow F5). The water or the brine which serves for the decomposition of the amalgam is led into the apparatus through conduit 40 (arrow F6). The lye resulting from the decomposition of the amalgam, and the emitted gas rise between walls 1 and 32 and are collected in space 42. They both leave the apparatus through conduit 41 (arrow F4) towards a separator (not shown in FIG. l).

Referring to FIG. 2, an installation has been given as an example for the electrolysis of saline solutions, which comprises the device shown in FIG. l, together with the necessary accessories.

The conductors 8 supply the electric current to the primary cell or main cell. The current leaves by conductor 2. The weakened 4brine mixed with bubbles of chlorine passes out under pressure through conduit 31 and reaches the separator .50. The chlorine is drawn oit by conduit 51 (arrow F10) and directed towards the washing and drying installation. A part of the brine is sent back to the primary cell or main cell by conduit 16. It is enriched on the way by the addition of concentrated brine coming from conduit 52 of the installation for the preparation (or the saturation) of the brine. A quantity of weekened brine, equal to that coming in through conduit 52, is drawn ofi at the separator by conduit 53. This brine can be sent directly to the installation for the preparation (or installation for saturation) of the brine, provided that the latter is equipped for working under pressure. When one wishes to employ an installation for the preparation of the ordinary brine, working at atmospheric pressure, it is preferable to cool the hot brine from conduit 531 below C. so as to avoid a rough emission of the steam during the expansion. The cooling of the weak lbrine is carried out in heat exchanger 54, which warms up the fresh brine of conduit 52. The cooled weak brine is expanded to atmospheric pressure in pressurereducing device 55 and passes into a further separator 56. The chlorine is evacuated through conduit 57 and the brine is directed towards the installation for the preparation of the brine through conduit 58. A heating device 59 enables the temperature of the brine in separator 50 to be regulated. An overow 60 enables the level'of brine to be maintained and to exchange charge of brine, if necessary, without stopping the cell.

The cell can work either by natural circulation or by forced circulation, since conduit 31 conveys weak lbrine containing gaseous chlorine, which is lighter than the supplying brine.

The mercuryreaches the primary or main cell through conduit 11 and the amalgam passes'out of the cell through conduit 151. It is directed towards a separator 70.

The amalgam to be decomposed is directed into the secondary cell, through the conduit 34. It flows down tangentially to the wall of the decomposer and meets a counter-current of water coming from the conduit 40. The metallic mercury is drawn off through the conduit 39 and directed towards separator 70 rwhere it is mixed with the amalgam coming from conduit 15.

A pump 71 evacuates this low-concentrated mixture and delivers it through the conduit 11 to the primary cell or main cell and through conduit 34 to the secondary cell (or decomposer).

The alkaline lye and the hydrogen which are formed in the decomposer pass out through conduit 41 and are directed to separator 72. The hydrogen is separated and evacuated by conduit 73. The lye is evacuated out of the separator by conduit 74. In this case also, a recirculation of the lye can be provided through conduit 76. Addition of fresh water is effected by conduit 77. A conduit 75 enables also the outgassing of separator 70.

It will of course be understood that the foregoing description has lbeen given by way of explanation but not in any limitative sense and that modifications can be made to the above forms of embodiment and they can be cornbined in different ways, without thereby departing from the scope of the invention.

We claim:

1. In an installation for the electrolysis of saline solutions, especially of equeous solutions of alkali chlorides, of the type comprising on the one hand an electrolysis cell in which a lm of mercury in circulation is utilized as a cathode and on the other hand accessory apparatus necessary for theA cycle of operation among which at least a decomposing device is provided for the decomposition of the amalgam formed between said mercury and the metal of the said solution to be electrolysed, the improvement which is constituted lby:

a primary cell with a truncated form and a vertical axis, said primary cell comprising an inner anodic metallic surface and an outer cathodic metallic surface, said surfaces being coaxial surfaces of revolution and the said cathode surface having a frustoconical shape;

a decomposing device mounted coaxially with and surrounding the said primary cel-l and comprising an outer surface of revolution supporting internally a plurality of decomposition grates adapted to regenerate the mercury contained in said amalgam, and means for owing said amalgam downwardly in a thin film between said grates and the cathode of the main cell.

2. In an installation for the electrolysis of saline solution, the improvement as claimed in claim 1, in which the said decomposition grates in the decomposing device are graphite pellets.

3. In an installation for the electrolysis of saline solutions, especially of equeous solutions of alkali chlorides, of the type comprising on the one hand an electrolysis cell in which a film of mercury in circulation is utilized 4 as a cathode and on the other hand accessory apparatus necessary for the cycle of operation among which at 4least a decomposing device is provided for the decomposition of the amalgam formed between said mercury and the metal ofthe said solution to be electrolysed, the improvement which is constituted by:

a primary cell with a truncated form and a vertical axis, said primary cell comprising an inner anodic metallic surface and an outer cathodic metallic surface, said surfaces being coaxial surfaces of revolution and the said cathodic surface having a frustoconical shape; Y

a decomposing device mounted coaxially with and surrounding the said primary cell and comprising an outer surface of revolution supporting'` internally a plurality of decomposition grates adapted to regenerate the mercurycontained in Said amalgam, means for flowing said amalgam downwardly in a thin film between the said grates and the cathode of the main cell;

vmeans for imparting to the mercury, before it spills over on to the cathode, a tangential velocity component whereby said mercury flows towards the -botl tom of said cell under the combined effect of gravity and said tangential component;

means for imparting to the saline solution to be electrolysed which enters the bottom of said cell, a tangential velocity component which is given to it before it arrives on the active surface of the anode, whereby the solution then rises into the space comprised between the two said electrodes and the said tangential components of the mercury and of the saline solution communicating respectively to the latter movements of .rotation in the same direction;

and means for imparting to the amalgam formed in the primary cell which enters the top of the decomposing device a tangential velocity component before it flows down on the decomposition grates.

4. In an installation for the electrolysis of saline solution, the improvement as claimed in claim 3, in which the said means for imparting tangential velocity components respectively to the mercury, to the saline solution and to the amalgam are constituted by annular spaces.

5. In an installation for the electrolysis of saline solutions, especially of aqueous solutions of alkali chlorides, of the type comprising on the one hand an electrolysis cell in which a film of mercury in circulation is utilized as a cathode and on the other hand accessory apparatus necessary for the cycle of operation among which at least a decomposing device is provided for the decomposition of the amalgam formed between said mercury and the metal of the said solution to be electrolysed, the improvement which, is constituted by:

a primary cell with a truncated form and a vertical axis, said primary cell comprising an inner anodic metallic surface and an outer cathodic metallic surface, said surfaces being coaxial surfaces of revolution and the said cathodic surface having a frustoconical shape; l

a decomposition device mounted coaxially with and surrounding the said primary cell and comprising an outer surface of revolution supporting interally a plurality of decomposition ,grates adapted to regenerate the mercury contained in said amalgam, means for flowing said amalgam downwardly in a thin film between said grates and the cathode ofthe main cell;

means for imparting to the mercury, before it spills over on to the cathode, a tangential velocity component whereby said mercury flows towards the bottom of said cell under the combined effect of gravity and said tangential component;

and vmeans for imparting to the saline solution to be electrolysed which enters the bottom of said cell, a tangential velocity componentwhiclris given to it before it arrives on the active surface of the anode,

whereby the solution then rises into the space comprised between the two said electrodes and the said tangential components of the mercury and of the saline solution communicating respectively to the latter movements of rotation in the same direction;

and means for imparting to the amalgam formed in the primary cell which enters the top of the decomposing ldevice a tangential velocity component before it flows down on the decomposition grates;

senarator means by which the gas normally liberated at the anode is separated from the weakened saline solution;

heating means for providing the desired temperature in said separator means;

means for saturating said weakened saline solution;

and separator means adapted to separate the mixture containing on the one hand the lye resulting from the decomposition of the amalgam and the lye ofthe countercurrent rising up, and on the other hand the gas produced in the decomposer by the combination of the alkali metal with water.

References Cited FOREIGN PATENTS 8/ 1964 France. 6/ 1954 Great Britain. 9/ 1963 Japan.

HOWARD S. WILLIAMS, Primary Examiner.

D. R. VALENTINE, Assistant Examiner. 

1. IN AN INSTALLATION FOR THE ELECTROLYSIS OF SALINE SOLUTIONS, ESPECIALLY OF EQUEOUS SOLUTIONS OF ALKALI CHLORIDES, OF THE TYPE COMPRISING ON THE ONE HAND AN ELECTROLYSIS CELL IN WHICH A FILM OF MERCURY IN CIRCULATION IS UTILIZED AS A CATHODE AND ON THE OTHER HAND ACCESSORY APPARATUS NECESSARY FOR THE CYCLE OF OPERATION AMONG WHICH AT LEAST A DECOMPOSING DEVICE IS PROVIDED FOR THE DECOMPOSITION OF THE AMALGAM FORMED BETWEEN SAID MERCURY AND THE METAL OF THE SAID SOLUTION TO BE ELECTROLYSED, THE IMPROVEMENT WHICH IS CONSTITUTED BY: A PRIMARY CELL WITH A TRUNCATED FORM AND A VERTICAL AXIS, SAID PRIMARY CELL COMPRISING AN INNER ANODIC METALLIC SURFACE AND AN OUTER CATHODIC METALLIC SURFACE, SAID SURFACES BEING COAXIAL SURFACES OF REVOLUTION AND THE SAID CATHODE SURFACE HAVING A FRUSTOCONICAL SHAPE; A DECOMPOSING DEVICE MOUNTED COAXIALLY WITH AND SURROUNDING THE SAID PRIMARY CELL AND COMPRISING AN OUTER SURFACE OF REVOLUTION SUPPORTING INTERNALLY A PLURALITY OF DECOMPOSITION GRATES ADAPTED TO REGENERATE THE MERCURY CONTAINED IN SAID AMALGAM, AND MEANS FOR FLOWING SAID AMALGAM DOWNWARDLY IN A THIN FILM BETWEEN SAID GRATES AND THE CATHODE OF THE MAIN CELL. 